VHDL - 限定表达式必须与上下文隐含的表达式类型相匹配 [英] VHDL - Qualified Expression must match the type that is implied for the expression by context

问题描述

这个问题是对我的最后一个问题.

正如我之前提到的，我正在尝试连接到经典的 HD44780 LCD.我已经实现了本地 ram，我将希望在显示器上显示的数据写入其中.

As I mentioned before, I'm trying to interface to a classic HD44780 LCD. I have implemented local ram to which I write the data I wish to show up on the display.

ram 是这样定义的(与上一个问题略有不同):

The ram is defined this way (slight change from last question):

type ram_type is array (integer range <>) of std_logic_vector(7 downto 0);
signal lcd_mem : ram_type(0 to 16*2-1);

我想在 LCD 的某个位置显示一堆常量字符和一个数字，我尝试通过这种方式直接写入 lcd_mem 来做到这一点:

I would like to display a bunch of constant characters and a number in a certain location on the LCD, I tried doing this by writing directly to lcd_mem this way:

lcd_mem <= (0 => x"45", 1 => x"72", 2 => x"72", 3 => x"6F", 4 => x"72", 5 => x"73", 6 => x"3A", 15 => x"30",    16 => x"54", 17 => x"58", 18 => x"3A", 30 => x"4D", 31 => x"3A", others => x"20");

第 79 行:

lcd_mem(22 to 28) <= get_ascii(1234567); --to_integer(unsigned(n_bits(39 downto 20)))

整数 1234567 稍后将被 to_integer 注释替换.

the integer 1234567 will later be replaced by the to_integer comment.

我已经编写了 get_ascii 函数，该函数应该通过将 0x30 添加到 bcd 表示将整数转换为 bcd 表示而不是 ascii.这是函数的一部分:

I have written the get_ascii function which is supposed to convert the integer into bcd representation and than to ascii by adding 0x30 to the bcd representation. Here is a part of the function:

variable num    : ram_type(0 to 16*2-1);
variable temp   : std_logic_vector(number'range);
variable bcd    : unsigned ((4*7-1) downto 0) := (others => '0');
.
.
.
num(0) := std_logic_vector(bcd(3 downto 0) + x"30");
num(1) := std_logic_vector(bcd(7 downto 4) + x"30");
num(2) := std_logic_vector(bcd(11 downto 8) + x"30");
num(3) := std_logic_vector(bcd(15 downto 12) + x"30");
num(4) := std_logic_vector(bcd(19 downto 16) + x"30");
num(5) := std_logic_vector(bcd(23 downto 20) + x"30");
num(6) := std_logic_vector(bcd(27 downto 24) + x"30");          
return num;

编译时出现以下错误:

错误 (10511): display_ber.vhd(79) 处的 VHDL 限定表达式错误:限定表达式中指定的 get_ascii 类型必须与上下文隐含的 ram_type 类型匹配

Error (10511): VHDL Qualified Expression error at display_ber.vhd(79): get_ascii type specified in Qualified Expression must match ram_type type that is implied for expression by context

我无法安静地理解消息的含义.我尝试定义一个更短的 ram_type(0 到 6) 变量来接收来自 get_ascii 函数的值，但这没有帮助.

I can't quiet understand the meaning of the message. I have tried defining a shorter variable of ram_type(0 to 6) to receive the value from the get_ascii function but that didn't help.

推荐答案

好吧，这显然是因为我在包和架构中都定义了类型ram_type".

Ok, apparently this happen because I defined the type "ram_type" in both the package and the architecture.

删除架构中的ram_type"定义后，错误消失了.

After deleting the "ram_type" definition in the architecture the error is gone.

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